France's Tatiana Golovin sent home favourite Venus Williams tumbling out of the Bausch & Lomb Championships.
Golovin is still trying to win her first tour title
Seeded eighth, Golovin hammered the unseeded Williams 6-2 6-3 in Amelia Island to set up a semi-final against fellow 19-year-old Ana Ivanovic.
"I put a lot of pressure on her right from the start," said Golovin.
"I was getting everything back. When she kind of came back, I fought through that. It's one of the better matches I've played all season so I'm happy."
Golovin also won their only previous meeting in 2005 when Williams was defending her title in Charleston, South Carolina.
Williams, who has won five Grand Slam tournaments in her career, is playing only her third tournament this year as she fights back from a wrist injury that kept her off court for eight months.
On a day of shocks, sixth seed Ivanovic beat second seed Jelena Jankovic 7-5 6-3 and Sybille Bammer saw off third seed Daniela Hantuchova 2-6 6-2 6-2.
Bammer, from Austria, will play top seed and defending champion Nadia Petrova, who beat Dinara Safina 6-4 7-5.